Doping and microwave power effects in the preparation of n-type SiC:H films using ECR-CVD

This paper reports the deposition of hydrogenated silicon carbide (SiC:H) films using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) technique. Using this technique, SiC:H films were prepared from a mixture of methane, silane and hydrogen, with phosphine as the doping gas. The effects of changing the phosphine fraction on the optical bandgap, activation energy and conductivity were investigated in films deposited at two different microwave powers of 150 W and 600 W, respectively. The effects of changes in the microwave power (from 150 W to 900 W) on the characteristics of the phosphorus-doped films were also investigated. An increase in the microwave power and high phosphorus doping fractions enhanced the formation of the silicon microcrystalline phase in the films. Films having a strong silicon microcrystalline phase exhibited relatively small changes in the optical bandgap. The film conductivity increased rapidly followed by saturation as the microwave power or phosphorus doping fraction was increased. Correspondingly, the activation energy decreased and saturated suggesting an effect from dopant saturation. The results showed that good phosphorus doping efficiency can be obtained in SiC:H films deposited at high microwave power. (C) 1997 Elsevier Science Ltd.